The high voltage test

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Safety tests are mandatory and are part of every final inspection of your electrical product.
Learn the most important facts about high voltage test in a nutshell.
We explain the WHY, WHERE, HOW, and also the potential dangers!
And if you want to learn more, you can download more detailed information at the bottom of this page for free!

_RIso or HV AC?

The basic approach of high voltage test very similar to insulation resistance testing. This is because both test methods focus on the quality of the insulation.
This can be done by measuring the insulation resistance or by testing the dielectric strength with high voltage and simultaneously measuring the leakage current.

However, the high voltage test even more "stressful" (intensive) for the device under test. It reveals insulation weaknesses very clearly. On the other hand, it has the disadvantage that it is not possible measurement insulation resistance precisely in MΩ or GΩ. It may therefore be advisable to carry out both tests one after the other.

The WHY?

Safe insulation is the key protective measure for ensuring electrical safety. It ensures that the operator touch operator live conductors and that no short circuit can occur between the conductors or to the housing of the equipment. If this were to happen, a life-threatening current could operator through the operator when they touch the housing. Of course, the protective earth conductor ensure that this does not happen. But in the worst case, it could also be defective. And it would only prevent the effect, not the cause.

to ensure all this, the insulation must function perfectly! And this must high voltage test proven and documented by you before delivery of the electrical product by means of a high voltage test .

This test is a random inspection. This means that every item, i.e. every single electrical product you place on the market, high voltage test a high voltage test .

The WO?

As a general rule, there must be good insulation between live conductors or between these and housing components. Typically, electrical conductors are insulated against dangerous contact, i.e., they are covered with insulating material. However, this protective covering must be removed at the latest when the electrical conductor is connected to other electrical components. At these points, insulation is ensured by maintaining a safe distance. This involves safety distances through air and creepage distances.

In addition, live conductors can also be insulated from each other using casting compounds, insulating films, or solid materials, for example.
When is which type of insulation used?
This always depends on the design of the electrical product and the type of requirements, such as high temperatures or mechanical stress, etc.

It is certainly understandable that insulation in a light fixture, an iron, an electric motor a high-voltage insulator in a power plant has very different requirements and designs.
This diversity therefore results in quite complex electrical insulation structures on a case-by-case basis.

The HOW?

Since the insulation has "something to do with voltage, voltagethe test is performed with a defined test voltage level. This can be device under test to the device under test in a ramp-shaped increase or directly at full level.

The aim is to measurement the current through the insulation, as this is the evaluation criterion for the insulation. It must not exceed a specified maximum current.
The upper limit of the current can vary greatly from product to product. There is little to nothing to be found in the standards regarding this limit. And there is a good reason for this – because the amount of current depends heavily on the capacitive component in the insulation.

Depending on the design of the product and its use in different regions/continents, the standards specify the TEST VOLTAGE, the minimum power required from the high-voltage source, and the test duration. They also specify whether the high voltage must be potential-free.

High voltage resistance is often measured sequentially between all conductors involved. These can be combined groups of conductors as well as individual conductors and, of course, the housing or housing parts. It quickly becomes apparent that, depending on the complexity of the electrical product, the test run at a wide variety of locations.
This could be done by scanning the test points with a test probe – an approach that can quickly prove to be time-consuming and costly.
For this reason, complex tests have been carried out automatically and freely programmable at any test points using the SCHLEICH matrix for 25 years:

SCHLEICH switch flexibly in 2- and 4-wire technology. The 4-wire technology is particularly important in automated systems and plants. It guarantees reliable contact control of the TEST VOLTAGE thus process reliability.

With such a wide range of requirements, it is of course ideal to use a testing device that covers as many of the global standards as possible.
That is our strength.

The Test current

Does insulation always consist of insulation resistance a capacitor? Why a capacitor? It wasn't even installed? ...

The test always takes place between two electrical conductors/poles. In abstract terms, these two poles form two opposing metal plates. The insulation is located between them. This structure corresponds to that of a capacitor. As a result, the entire insulation structure also behaves in a highly capacitive manner.

The high voltage test is performed with alternating voltage. This causes a current TEST VOLTAGE on the frequency of the TEST VOLTAGE to flow in the capacitive portion of the insulation. The magnitude of the leakage current is proportional to the magnitude of the Capacitance.
These are physical conditions that have nothing to do with the good or bad insulation properties of the test object. They, and of course the standard, specify the maximum permissible current.
The decisive factor now is the power of the high-voltage source. It must be able to supply the required current. Otherwise, the high voltage test would high voltage test be feasible.

The DANGER?

If an alternating current of less than 3 mA flows through the human body, it is classified as harmless.
If a high-voltage source can only supply a maximum of 3 mA, it is therefore considered to be safety-current-limited and harmless. Special protective measures are then not necessary.

However, a current of 3 mA is high voltage test insignificant in most high voltage test . Due to the capacitive effect, many electrical products require a significantly higher Test current. As mentioned, this is not a knockout for the device under test but it is dangerous for the operator. This is because the high-voltage source is often Test current for Test current 100 mA. Appropriate protective measures are therefore essential.

These include:

• electrically isolated high voltage
• Barricading of the test site
• Safety test guns
• Two-hand start with corresponding safety relays
• Test cage or test cabin – monitored by two circuits with approved safety relays and, if necessary, a secure interlock
• Compliance with performance level PLe, SIL3, Cat4, etc.

Performance Level PLe, SIL3, Cat 4 …

The requirements for safety technology are correspondingly high for a Test current 3 mA. The relevant international standards must be complied with worldwide.

SCHLEICH testers meet these requirements!

It should be noted that there are various testing devices on the international market that may appear to be a bargain, but do not comply with the legally required safety regulations of EN50191/VDE0104!

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Our mission – knowledge, knowledge, knowledge ... Those who have a sound technical and normative understanding of testing methods will get the most out of their testing equipment.
– Dipl. Ing. Martin Lahrmann

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